The present invention relates to flexible polyurethane foams, suitable for use in the automobile industry, which have a considerably reduced fogging effect because they are manufactured using polyester polyols in which the proportion of volatile residues has been reduced or in which the volatile residues have been eliminated.
In the industry of manufacturing polymeric materials for the automobile industry there is a growing preoccupation with the fogging of the front and rear windshields and side windows of cars because of volatile residue condensation that accompanies these polymeric materials. This problem, which is known in the industrial sector as the fogging effect, as well as the unpleasant characteristic odor produced by the evaporation of the volatile residues and its possible toxic consequences, is produced by conditions in which the interior of the vehicle is subjected to relatively high temperatures, for example when closed vehicles are exposed to the sun, causing the volatile substances to evaporate and condense on the colder surfaces of the windows.
As a result, the automobile industry imposes increasingly stricter requirements on the suppliers of the polymeric materials, so that the polymeric materials used in the interiors of automobiles must currently have a fogging effect less than 1 mg in the gravimetric test according to Standard DIN 75201 B.
Recent publications have disclosed the influence of some additives on the fogging effect produced by flexible polyurethane foams made of polyether polyols. C. Blundell, and J. Wuestenenk, Utech'90 Proceedings, 76-79 (1990) have shown the influence of flame retarding agents, and K. Diblitz and D. Hoell, Utech'90 Proceedings, 80-85 (1990) have done the same with amine-type catalysts.
If they are well formulated, flexible polyurethane foams made using polyether polyols exhibit fogging values that are lower than those made using polyester polyols. However, foams made using polyester polyols provide advantages including better mechanical properties, a better cellular structure, greater resistance to oils and oxidation, and furthermore are easier to flame roll, have a lower total emission of gases and are easier to recycle. Therefore, the need remains to solve the problem of providing the automobile industry with flexible polyurethane foams made using polyester polyols that, without losing their excellent properties, have reduced levels of fogging that fulfill the strict requirements currently imposed by the industry.